
/* 清除浏览器默认边距，
使边框和内边距的值包含在元素的height和width内 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
/* flex布局，让内容垂直和水平居中 */
body {
   display: flex;
   justify-content: center;
   align-items: center;
   min-height: 100vh;
   background: #000;
}
/* flex布局，让内容垂直和水平居中，超过的部分换行显示 */
.container {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
}
/* 按钮的基本样式 */
.container a {
    position: relative;
    padding: 15px 30px;
    margin: 50px;
    border: 2px solid #0f0;
    font-size: 18px;
    font-weight: 600;
    text-decoration: none;
    letter-spacing: 5px;
    color: #fff;
    filter: hue-rotate(calc(var(--x) * 60deg));
    transition: 0.5s;
}
/* 鼠标经过时改变按钮样式 */
.container a:hover {
    transition-delay: 1.5s;
    color: #000;
    box-shadow: 0 0 10px #0f0,
                0 0 20px #0f0,
                0 0 40px #0f0,
                0 0 80px #0f0,
                0 0 160px #0f0,
                0 0 320px #0f0;
}
a span {
    position: relative;
    z-index: 10;
}
/* 通过伪元素::before实现按钮左边的线 */
.container a::before {
    content: "";
    position: absolute;
    left: -20px;
    top: 50%;
    transform: translateY(-50%);
    background: #0f0;
    width: 20px;
    height: 2px;
    box-shadow: 5px -8px 0 #0f0,
                5px 8px 0 #0f0;
    transition: width 0.5s, height 0.5s, left 0.5s,
                 box-shadow 0.5s;
    transition-delay: 0s, 1s, 0s, 0.5s;
}
/* 鼠标经过时改变线条的样式 */
.container a:hover::before {
    width: 60%;
    height: 100%;
    left: -2px;
    box-shadow: 0 0 0 #0f0,
                0 0 0 #0f0;
}
/* 通过伪元素::after实现按钮右边的线 */
.container a::after {
    content: "";
    position: absolute;
    right: -20px;
    top: 50%;
    transform: translateY(-50%);
    background: #0f0;
    width: 20px;
    height: 2px;
    box-shadow: -5px -8px 0 #0f0,
                -5px 8px 0 #0f0;
    transition: width 0.5s, height 0.5s, right 0.5s,
                 box-shadow 0.5s;
    transition-delay: 0s, 1s, 0s, 0.5s;
}
/* 鼠标经过时改变线条的样式 */
.container a:hover::after {
    width: 60%;
    height: 100%;
    right: -2px;
    box-shadow: 0 0 0 #0f0,
                0 0 0 #0f0;
}
